1. Field of Invention
The present invention relates to a device for diagnosis and/or therapy of a selected portion of a body by optical reflectance or optical transmission, according to the preamble of claim 1.
Monitoring of certain physiological characteristics of a patient is an inevitable tool in medicine for diagnosis and therapy. Thus, a variety of devices has been developed for measuring such characteristics.
The technique of near infrared spectroscopy (NIRS) is used for various applications, amongst others for monitoring hemodynamics and oxygenation of a selected portion of a body, as e.g. of a specific organ like the brain. Thereby, light in the near infrared spectral domain is emitted into the selected portion of tissue of the body by a light transmitter means. A light receiver means detects the amount of transmitted and/or reflected light. The ratio of absorbed and scattered light with respect to the emitted light can then be determined, from which one or more of the above mentioned physiological characteristics can be calculated.
2. Description of Related Art
Such a device applicable for NIRS measurements is disclosed in U.S. Pat. No. 4,510,938. An assembly of the device includes a base support pad having two socket holes in which module sockets can be installed. These module sockets are formed with an open base end and provide housings for so called optical modules. Each optical module includes an optical fibre cable made up of a bundle of optical fibres which couples through quick disconnect optical coupling, leading directly to a light source and a processing circuitry. Within the optical modules, the optical fibres terminate with a right angle shaped terminal end destined for deflecting an optical light signal at least approximately of an angle of 90°. The terminal end has a slightly protruding portion with respect to the open base end of the module socket, establishing a ground optical face. Furthermore, the terminal end of the fibre bundles can provide both, a near-infrared light source terminal destined for bringing light to the point of light entry of the selected portion of the body, or a near-infrared light detector terminal being destined for collecting and transmitting reflected/transmitted light for further processing and calculations.
The optical modules can be fully nested in their respective module sockets. Therefore, the module sockets include an open slot for receiving the optical fibre cable of the optical module which leads to the light source and the processing circuitry.
Furthermore, the base support pad is formed with two parallel slits leading from the socket holes to an edge of the base support pad. These slits are intended, amongst others, for facilitating the assembling of the base support pad and the module sockets together with their respective optical modules. For securing the module sockets on the base support pad, each of the module sockets is provided at the open base end with three radially extending, thin, and flexible tabs. A double sided adhesive tape is attached on each tab as a means for affixing the respective module socket on the base support pad.
Shielding of ambient light from the optical light modules, and especially from the ground optical face, is crucial for an accurate detection of the amount of transmitted and/or reflected light. Thus, e.g. in U.S. Pat. No. 4,510,938, different light shielding means are disclosed. Double-sided, annular-shaped, and pressure sensitive adhesive tapes of light shielding material are employed on the optical modules and are mounted around the respective ground optical faces in order to provide the desired shielding of ambient light. Additionally, when the optical modules are assembled in their respective module sockets which are affixed by the three radially extending tabs on the base support tab, an auxiliary pad composed of light shielding material which is provided with double-sided adhesive tape is firmly secured over the module sockets and the optical cables. Finally, an overall light shielding cape is affixed over the whole assembly.
A different embodiment compared to the optical modules as described above is disclosed in U.S. Pat. No. 6,343,177 where an integrated fibre terminal and reflector system are presented for transmitting and/or receiving optical signals that are off-axis relative to a terminated optical fibre. Thereby, at least an approximately right angle shaped deflection of the optical signal is accomplished by said optical reflector system without the need for bending the optical fibre within the fibre terminal.
A further embodiment of a device for measuring cerebral hemodynamics and oxygenation invasively is disclosed in EP 1 301 119. It uses passive illuminating and receiving means, i.e. at least two optical transmission means, each comprising one or more optical fibres. A first transmission means transmits light from its proximal to its distal end, i.e. from a light source to a patients head and brain tissue. A second transmission means transmits light from its distal to its proximal end, i.e. from the patient's head and brain tissue to a detection unit. The transmission means are encapsulated by a coating forming an elongated, flat structure which fixes the spatial arrangement of the transmission means. Thereby, the distal end of each transmission means is connected to a deflection means encapsulated by the same coating, being at least in a region of entrance respectively exit of the deflection means optically transmissive to light at wavelengths used. The deflection means are destined for deflecting light transmitted by the transmission means from a direction of transmission, preferably by an angle of 60 to 120°. Preferably the light is deflected by approximately 90° with respect to the direction of transmission. Since optical fibres are small in diameter and deflecting means can be manufactured small in size, the device destined for minimal invasive measurements can be assembled with a width of preferably less than about 20 mm and a thickness of preferably less than about 5 mm.